Four ports which have slightly different shapes have been applied to 3-valve MPI SI engine to develop Axially Stratified Lean Combustion engine. The purpose of port modification test was to investigate the effects of swirl ratio and direction on engine performance and emissions.In the engine test injection characteristics, i.e. timing, flow rate, direction as well as port design significantly effected on the engine combustion. Especially, it was observed that injection timing was the most important factor for combustion stability, but its effect on performance has some differences in accordance with the port designs.To verify the relationship between port shape and injection timing, in-cylinder gas was sampled by high speed gas sampling device varing injection timing through whole intake and compression,. strokes at spark plug position and analyzed by gas chromatography. It was assumed that the behavior of fully atomized fuel in the cylinder represented the air motion in intake and compression strokes. For the constraints of the sampling position, the exact tracking of fuel behavior is impossible, but with referring the visualization result concurrently it could be said that not only swirl but also other macro air motion existed in the cylinder and this air motion played almost the same important role for axially stratified charging as well as swirl in case of the port which had relatively low swirl.